ε-Caprolactam is an important chemical material that can be used as a material for nylons and the like, and is industrially produced worldwide. It is mostly used as a material for Nylon 6, which is a polyamide.
As an industrial production method for ε-caprolactam, a production method using the Beckmann rearrangement reaction with fuming sulfuric acid from cyclohexanone oxime has been widely employed. However, there is a problem that a large amount of ammonium sulfate is produced as a by-product in the neutralization step in the Beckmann rearrangement reaction. On the other hand, as production methods for ε-caprolactam that do not produce ammonium sulfate as a by-product, a method in which combination of ammoximation and the gas-phase Beckmann rearrangement reaction is used from cyclohexanone (Non-patent Document 1) and a method in which ε-caprolactam is brought into contact with a catalyst in the presence of ammonia (Patent Document 1) have been proposed.
All of the above production methods for ε-caprolactam use crude oil as the original material. From the viewpoint of possible depletion of oil resources in the future, and the problem of global warming due to emission of greenhouse gases by mining and use of fossil resources, development of methods for producing caprolactam using alternative materials is necessary. In particular, development of a method for producing caprolactam from biomass, which is a regenerative resource, or from substances inducible from biomass resources, has been demanded.
Several methods for producing ε-caprolactam from substances inducible from biomass resources have been reported so far. For example, Patent Document 2 discloses a method for producing ε-caprolactam through ε-caprolactone using 5-hydroxymethylfurfural as a material. Patent Document 3 discloses a method for producing ε-caprolactam by using adipic acid as a material and reacting it with hydrogen and ammonia. Patent Document 4 discloses a method for producing ε-caprolactam by using muconic acid as a material and reacting it with hydrogen and ammonia.